1.Most generally, the range of values within which an ADDRESS has meaning and can be guaranteed to be unique. In everyday life, for example, each street constitutes a separate address space so that the same number, 12, might be used to describe different houses in Acacia Avenue and Laburnum Grove.

2 The range of contiguous memory addresses allocated to a single TASK or PROCESS.

3 The full range of PHYSICAL addresses that a computer's processor can access, which is determined directly by the width of the processor's ADDRESS BUS: a 16-bit bus can address 65,536 words (216) while a 32-bit bus can address 4,294,967,296 words (232), which would correspond to 4 gigabytes if the machine uses BYTE-ADDRESSING.